There is an increasing tendency to provide mobility support for networks and protocols that have traditionally been aimed at fixed communication applications. For example, there is a desire to include mobility support for the popular Internet Protocol (IP) which is used in many communication networks and in particular there is a desire to increasingly base mobile cellular communication systems on infrastructure that uses IP as standardized by the Internet Engineering Task Force (IETF).
Accordingly, recent versions of the Internet Protocols have been developed or enhanced to provide mobility support for mobile nodes and networks.
Specifically, a mobility enhancement known as NEMO (NEtwork MObility) has been developed for Internet Protocol version 4 (IPv4) as e.g. described in K. Leung et al, “Network Mobility (NEMO) Extensions for Mobile IPv4”, draft-ietf-mip4-nemo-v4-base-06.txt, IETF Internet Draft, work in progress, 31 Oct. 2007, and for IPv6 as e.g. described in V. Devarapalli et al., “Network Mobility (NEMO) Basic Support Protocol”, IETF RFC 3963, Standards Track, January 2005.
Also, the Internet Protocol version 6 (IPv6) is being developed to inherently support mobility as e.g. described in D. Johnson et al., “Mobility Support in IPv6”, IETF RFC 3775, Standards Track, June 2004.
Accordingly, these networks allow a Mobile Entity (ME) to move between IP subnets in an IP infrastructure while maintaining its ongoing IP sessions. The supporting mobility protocols are defined for both IPv4 and IPv6, and rely on dynamic establishment of a bi-directional tunnel between the ME's current point of attachment (defined by the Care-of Address (CoA) for the ME) and its mobility anchor point (the Home Agent (HA)) in its home network. In the downstream direction, IP packets addressed to the ME (i.e. IP packets addressed to the ME's home address or to a destination address which matches the ME's mobile subnet (if the ME is a mobile router)) are intercepted by the HA and routed over the tunnel to the ME's CoA. Similarly, in the upstream direction, IP packets sourced by the ME (or by any of its attached nodes in case of a mobile router) are tunneled towards the HA, and from there routed to the destination.
In order to continue receiving traffic sent to its home address (HoA) when roaming to a foreign link, the ME will specifically send a message (requesting a binding of its HoA to its current CoA) to the HA. The message used to bind the HoA to the CoA is known as a Registration Request (RREQ) in MIPv4 and a Binding Update (BU) in MIPv6. The registration message is acknowledged by a Registration Reply (RREP) or Binding Acknowledgement (BA) message transmitted by the HA.
However, although this approach may enable or facilitate mobility, the process has some associated disadvantages and in particular the communication of registration/binding updates, the associated forwarding delays, and the tunnel initialization tend to degrade the performance of the mobile IP protocols during handovers of the ME between different sub-networks. Indeed, if the ME's handover frequency is high, the approach will result in significant communication overheads and handover delays. Furthermore, the associated signaling increases bandwidth usage and the complexity/processing requirement of the ME and HA.
Hence, an improved system would be advantageous and in particular a system allowing increased flexibility, improved mobility support/performance, facilitated operation, improved binding update operation and/or improved performance would be advantageous.